AB Float & Integers Question

Duwop

Member
Join Date
Sep 2007
Location
Alabama
Posts
37
Hello All,
I'm rather new to this site, so please forgive any dumbness.
I'm posting this in an effort to do a better job of my programming.
I've got some AB (micro 1200's & SLC's) PLC's communicatimg via radio & ethernet. The PLC's that comm via radio are my focus at the moment, all of which comm integers (modbus). I have some floating points that I'm currently putting into 2 integers then when it gets to a PLC that comms ethernet I put the integers back to Floating point for our SCADA.
If the radio PLC & the ethernet PLC are both SLC's, I'm just using a COP statement to go from floating pt to 2 integers & then back again with the same type of statement (which seems to be working fine).
If the radio PLC is a Micro 1200 & the Ethernet PLC is a SLC
(In the 1200) I'm using a CPW statement to go to integers, & in the SLC, I'm using 2 MOV statements to swap the low & high word (because it seems they are reversed in the SLC) then I'm using a COP statement to put the integers back to Floating Point.
Example: (in the Ethernet SLC 5/05 PLC)
MOV n16:12 to N7:11
MOV n16:13 to N7:10
COP N7:10 to F8:25 with a length of 2
This seems to work also BUT there an easier way for me to do this & is my thinking right on this???
 
Why modbus? Sence all processors are AB products why not use an AB protocol.(i.e DF1), Then just mgs floating point numbers. (i.e. F8:0)
Your SCADA software surely will support a AB protocol.
 
The PLC's and some of the radios were installed by another company.
There were some other PLC's & DCS's already in our system, so they did alot of modbus to join some of it because alot of the equipment needs
info from another. When it's Ethernet PLC's & they are AB's, I've been doing as you say, but some the radio's comm via modbus because the master radio PLC may be a SLC but there may be 12 remotes radios communicating to micro 1200's, Bristol Babcock 3350's, GE 90-30's, or SLC's, hence the modbus.
 
We have some Phoenix 900mhz radio gear in service for polling several KEP flow computers via a Prosoft serial modbus card in an SLC 5/05.

I understand your dilemma of being stuck sending integers back and forth as well as the modbus "swap" issue present in some manufacturer's gear, but I've found no other way of converting from Float/Integer than what you've described. Prosoft still lists this method in their manuals--the only way I can see that you could make it more efficient would be to use an indirect addressing scheme or something to reuse the same portion of ladder.
 
Thanks for the help.
Now that you mention it, We have MDS 900mhz radio gear with the master radio hooked to a Prosoft serial modbus card in a SLC 5/05 that is also
ethernets back to our SCADA.
 

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